This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations and terms are herewith defined:                3GPP third generation partnership project        DL downlink        EPS evolved packet system        E-UTRAN evolved UTRAN        GBR guaranteed bit rate        GPRS general packet radio service        HO handover        IE information element        IRAT inter radio access technology        ISHO intersystem handover        LTE long term evolution of 3GPP (also termed E-UTRAN, 3.9G or SAE)        MME mobility management entity        Node B base station or similar network access node        PCRF policy and charging rules function        PDP packet data protocol        QCI QoS class identifier        OoS quality of service        RAN radio access node        RTSP real time streaming protocol        SAE system architecture evolution        SDP session description protocol        SGSN serving GPRS support node        SIP session initiation protocol        TEID tunnel end point identifier        TFT traffic flow template        UE user equipment (e.g., mobile equipment/station)        UL uplink        UMTS universal mobile telecommunications system        UPE user plane entity (e.g., a combined LTE anchor and 3GPP anchor)        UTRAN UMTS terrestrial radio access network        
3GPP is standardizing the long-term evolution (LTE) of the radio-access technology which aims to achieve reduced latency, higher user data rates, improved system capacity and coverage, and reduced cost for the operator. An overview of the system architecture is shown in FIG. 1a which similarly reproduces FIG. 4.2.1-1 of 3GPP TS 23.401: GPRS Enhancements for E-UTRAN Access (Release 8), ver 1.3.0 (2007-10), and in FIG. 1b taken from 3GPP TR 23.882, herein incorporated by reference), wherein the aspects relevant to these disclosures concern handing over of a user device (e.g., mobile terminal/mobile station/handset) between a first type of network such as the LTE network shown and a different type of network such as for example a 2G or 3G network shown as UTRAN or GERAN in FIGS. 1a and 1b. This is termed generally an inter-RAT or intersystem handover since it is a handover between different radio access technologies RATs or systems. Inter-RAT handovers are challenging because the different systems have typically been developed with different tradeoffs and so they often operate such that analogous nodes such as base stations in the different systems operate with a different set of information requirements, and the different information is resident in different ones of the network nodes and user equipment.
One of those disparities as between at least LTE and 2G/3G networks is quality of service (QoS) support. QoS is implemented in SAE/LTE using network controlled and network initiated dedicated bearers. QoS is implemented in 3G/2G systems by packet data protocol PDP contexts, which are controlled by the mobile terminals. Since LTE is a new 3GPP system and still being finalized, there has not been a QoS problem with handovers between LTE and 2G/3G systems, and the inventors are aware of no mechanism in the prior art by which such a handover with proper QoS support might be accomplished.
Relevant to this disclosure are sections 5.4 through 5.5 of 3GPP TS 23.401: GPRS Enhancements for E-UTRAN Access (Release 8), ver 1.3.0 (2007-10). As used herein, a bearer is an information transmission path of defined capacity, delay or bit error rate, etc. as defined in 3GPP TR 21.905 v8.2.0 (or in subsequent versions thereof): Vocabulary for 3GPP Specifications. A multi-radio terminal as used herein (for brevity, a terminal or a UE) is a terminal which can be used in 2G and/or 3G as well as in LTE access networks. Such a terminal can be for example a network card used as a modem for a laptop computer or for a particular mobile handset such as current mobile phones.
For a proper handover, it is required that the target access system would have full QoS support for the terminal immediately when the terminal releases the connection to the old access system. During intersystem handover from SAE/LTE to 3G/2G, it is assumed that the LTE network controlled dedicated bearers would be changed or mapped to the 3G/2G terminal controlled PDP contexts. This requires that not only primary, but also requested secondary contexts are pre-established in the target 3G/2G access network before the terminal is released from the source LTE access network. In the current 3G/2G system, the secondary PDP context is created only if the terminal has requested it. Therefore the terminal has at all times knowledge of the secondary PDP context. If the target access system in a terminal handover is an LTE system and the old access system is a 3G/2G access system, then since the terminal being handed over has knowledge of its secondary PDP context, any dedicated bearers that are created would be in response to the terminal's request to the LTE network. But this raises several questions in order to properly support QoS in the handover. How does one ensure that all the necessary secondary contexts are created so that the proper dedicated bearers can be mapped to them? Said another way, it is important to avoid pre-establishing PDP contexts which are not supported by the UE, and to either pre-establish all of the UE supported PDP contexts in the handover preparation phase of indicate to the terminal in some other way which ones are not.
What is needed in the art is a way to address QoS for intersystem handovers so as to resolve the above issues.